The invention relates to a volumetric-flow measuring apparatus having a basic body which receives a measuring unit, and a measuring funnel from a foldable material, which is attached on the basic body, wherein the measuring funnel is convertible from a transport position to a use position.
Volumetric-flow measuring apparatuses of this type are known for example as volumetric flow hoods and are employed for measuring a volumetric flow through a supply-air or exhaust-air opening of a building ventilation plant.
To this end the measuring funnel by way of an air intake is placed onto the supply-air or exhaust-air opening of the building ventilation plant. Using the measuring unit, for example an anemometer, the volumetric flow through the supply-air or exhaust-air opening can thus be measured.
It is known for the measuring funnels to be configured from a foldable material, in order to fold up the measuring funnel into a transport position. In this transport position the measuring funnel occupies little space and is easily transportable.
It has emerged that large measuring errors may occur in the measurement of volumetric flow when the flow to be measured has a swirl. Measuring errors of this type may be present in the order of 50% or more of the measured values. It has, therefore, been proposed to use flow straighteners with which the air flow can be de-swirled in that fractions of the flow having a flow angle in relation to a longitudinal axis of the flow straightener that lies above a specific threshold value are oriented or diverted, respectively.
It has been proposed to this end in DE 10139542 B4 to directly dispose a louvre grid construction as a flow straightener on air-guide elements of a supply-air opening which is configured as a swirl distributor for the duration of the measurement. However, this necessitates separate assembly of the flow straightener prior to the measurement.
The invention is concerned with improving the useful properties of a volumetric-flow measuring apparatus.